When an affection which is against nature and violent occurs within us with intensity it is painful, whereas the return back to the natural condition, when intense, is pleasantCf. Rep. 583 C ff.,Phileb. 31 D ff.; and an affection which is mild and gradual is imperceptible, while the converse is of a contrary character. And the affection which, in its entirety, takes place with ease is eminently perceptible, but it does not involve pain or pleasure; such, for example, are the affections of the visual stream itself, which, as we said before,Cf. 45 B. becomes in the daylight a body substantially one with our own. For no pains are produced therein by cuttings or burnings